driver: Fix recompilation checking for exported defaults and COMPLETE pragmas

A {-# COMPLETE P, Q #-} pragma is associated with the pattern synonyms P
and Q during recompilation checking. Therefore, the existence of a
pattern synonym becomes part of the ABI hash for P and Q.

Then if a module uses these pattern synonyms and a complete pragma
changes, it will trigger recompilation in that module.

Fixes #25854 

and

Since the exported defaults are not associated with any identifier from
the module, they are just added to the export hash rather than
the fine-grained recompilation logic.

Fixes #25855